A friction agitation joining method, which is one type of solid-phase joining method, has advantages in that the method can be applied to various joining-members irrespective of the kind metallic materials and causes less thermal stress due to the joining. In recent years, this method has been used as a joining means for manufacturing a joined member used as a floor member, a wall member, a ceiling member, a suspension arm member, etc., for ships, automobiles and railroad cars.
A conventional friction agitation joining method will now be described with reference to FIG. 11, in which two plate-shaped joining-members made of aluminum alloy are integrally joined in a butted manner.
In FIG. 11, the reference numeral 110A denotes a conventional friction agitation joining tool. The joining tool 110A is provided with a columnar rotor 111 and a pin-shaped probe 113 having a diameter smaller than that of the rotor 111. The probe 113 is integrally protruded from a rotational center of an end face 112 of the end portion of the rotor 111. The end face 112 of the rotor 111 is formed into a flat surface perpendicular to the rotation axis Q′ of the rotor 111.
With the joining tool 110A, the probe 113 is rotated in accordance with the rotation of the rotor 111. The rotating probe 113 is inserted into a butted portion 103 of joining-members 101a and 101b so that the end portion of the rotating rotor 111 touches the surfaces of the joining-members 101a and 101b. Then, while maintaining this state, the end portion of the rotor 111 is advanced along the butted portion 103.
By the friction heat generated due to the rotation of the probe 113 and the friction heat generated due to the friction between the end face 112 of the end portion of the rotor 111 and the surfaces of the joining-members 101a and 101b, the joining-members 101a and 101b are softened at around the portion of the joining-members 101a and 101b where the end portion of the rotor 111 and the probe 113 contact. Then, the materials in the softened portion will receive the rotating force of the end portion of the rotor 111 and the rotating force of the probe 113 to be agitated and mixed. Furthermore, in accordance with the advance movement of the end portion of the rotor 111, the softened materials will be plastically fluidized to fill up a groove formed after the end portion of the rotor 111 and the probe 113 pass. Thereafter, the materials will be cooled and solidified by immediate loss of the friction heat. This phenomenon will be repeated in accordance with the advance movement of the end portion of the rotor 111 to thereby integrally join the joining-members 101a and 101b at the butted portion 103 (a joined portion 104). Thus, a joined member,can be obtained.
By the way, in this friction agitation joining method, when the end portion of the rotor 110 is advanced along the butted portion 103, the materials of the joining-members 101a and 101b softened by the friction heat tend to be pushed out toward the outer surfaces of the joining-members 101a and 101b by receiving the advancing pressure of the end portion of the rotor 111. This causes the following drawbacks. Joining defects (e.g., hollow portions) due to the lack of materials may occur in the joined portion 104. Burrs formed by the pushed out materials may occur on the surface of the joined portion 104. The thickness of the joined portion 104 may decrease due to the pushed out materials. Accordingly, a joined member with good joining condition cannot be obtained.
In order to solve the above-mentioned problems, conventionally, the joining operation has been performed as follows. As shown in FIG. 11, at the time of the advance movement of the end portion of the rotor 111, the rotation axis Q′ of the rotor 111 is inclined rearward relative to the joining direction (i.e., rearward to the moving direction) so that the advancing front edge of the end face 112 of the end portion of the rotor 111 is lifted up from the surfaces of the joining-members 101a and 101b. While keeping this inclined state, the end portion of the rotor 111 is advanced along the butted portion 103. In FIG. 11, the reference letter T′ denotes a normal line at the inserted position of the probe on the surfaces of the joining-members 101a and 101b. The reference letter θ′ denotes the inclined angle of the rotation axis Q′ to the normal line T′ when the rotation axis Q′ of the rotor 111 is inclined rearward relative to the joining direction.
In this method, the end portion of the rotor 111 is advanced while keeping the inclined state in which the advancing edge of the end face 112 of the end portion of the rotor 111 is lifted up from the surfaces of the joining-members 101a and 101b so that the materials of the joining-members 101a and 101b are held by the end face 112 of the rotor 111 to prevent the escape of the materials therefrom. Thus, the above-mentioned problems can be solved.
However, in the conventional joining tool 110A, since the end face 112 of the end portion of the rotor 111 was formed into a flat surface, it was difficult to hold the materials of the joining-members 101a and 101b by the end face 112.
Furthermore, according to this method, the end portion of the rotor 111 had to be advanced in a state that the rotation axis Q′ of the rotor 111 was inclined rearward relative to the joining direction. Therefore, it was difficult to perform the joining operation. The joining operation was particularly difficult when the joining portion curved along a circular line or the like.
The present invention was made in view of the above-mentioned technical background. The object of the present invention is to provide a friction agitation joining tool, a friction agitation joining method and a joined member manufacturing method, which can hold the materials of joining-members softened by the friction heat and can obtain a joined member with good joining condition.
Other objects and advantages of the present invention will be apparent from the following preferred embodiments.